One of the world's best overclockers, Toppc, has used some Kingston HyperX Predator DDR4 RAM to reach an insane 4351MHz, breaking some records along the way. Toppc achieved 4.35GHz on the Kingston DDR4 RAM in single-channel mode, all the way from its default clocks of 2133MHz.
We don't know what cooling was used on the RAM, but we suspect LN2 was used to push over double the clock speed, while the Intel Core i7-5960X processor used was clocked all the way down to 1631MHz. Just a single core was enabled, with the other seven cores and the CPU's internal Hyper-Threading technology also disabled.
There's not much reason to do this, as a quad-channel kit of DDR4 was 108.8GB/sec bandwidth at 3.4GHz while the single-channel stick at the, albeit impressive 4.35GHz, has bandwidth of just 34.8GB/sec. But for getting that overclocking trophy, why not, eh?